A randomized trial of rosiglitazone therapy in patients with inadequately controlled insulin-treated type 2 diabetes

Insulin resistance: from predisposing factor to therapeutic target in type 2 diabetes

BACKGROUND

Insulin resistance contributes to the pathogenesis of type 2 diabetes and is closely linked with cardiovascular risk factors and premature cardiovascular disease.

OBJECTIVE

The purpose of this paper was to review the importance of insulin resistance as a core defect in type 2 diabetes, a potential contributor to accelerated atherosclerosis, and a potential target for insulin-sensitizing agents.

METHODS

Articles considered for inclusion in this review were identified through a search of MEDLINE/PubMed for reports published from 1966 to April 2003. Search terms used were insulin resistance, diabetes, insulin sensitivity, obesity, cardiovascular disease, metformin, thiazolidinediones, pioglitazone, rosiglitazone, and troglitazone.

RESULTS

An overview of the epidemiology, natural history, and pathophysiology of type 2 diabetes is provided, with a focus on insulin resistance and a related discussion of the impact of current therapies used to treat insulin-resistant patients. In particular, information on insulin-sensitizing agents-metformin and the currently available thiazolidinediones (TZDs), pioglitazone and rosiglitazone-is presented. Although metformin has been shown to indirectly reduce insulin resistance, TZDs are the only available agents that have been shown to directly lower insulin resistance.

CONCLUSIONS

Recent evidence indicates that metformin, pioglitazone, and rosiglitazone may improve the dyslipidemic profile, reduce vascular inflammation, and improve endothelial dysfunction, all of which may be particularly important to physicians seeking treatment options to prevent or reduce cardiovascular complications in patients with type 2 diabetes.

The management of the obese diabetic patient

The prevalence of obesity and diabetes is increasing in the United States and worldwide. These diseases are predicted to explode to epidemic proportions, unless appropriate counteractive measures are taken. Several large studies (DCCT, UKPDS, Kumamoto) clearly showed that intensive glycemic control in the diabetic patient reduced microvascular complications and improved mortality. Despite this, the NHANES III showed that only 50% of diabetics have been able to achieve a HgbAic level that is less than 7%; this suggests the need for a re-evaluation of our approach to these patients. The management of the obese diabetic patient involves glycemic control and weight reduction. These goals are particularly difficult to achieve in the obese diabetic patient because progressive beta-cell dysfunction and increasing insulin resistance necessitates the administration of increasingly higher dosages of insulin, which, in turn, promotes weight gain. A vicious cycle may ensue. Lifestyle modifications with diet and exercise are an essential part of the management of the obese diabetic patient. These measures alone are often insufficient and concomitant pharmacologic therapy is usually required to achieve glycemic and weight control. Oral agents that improve glycemia, decrease insulin resistance, and limit weight gain are desirable. Because of the progressive nature of diabetes, glycemic control with monotherapy often deteriorates over time, which necessitates the addition of other pharmacologic agents, including insulin. When insulin therapy is required in the treatment of the obese diabetic patient, combinations with oral agents that have been shown to minimize the amount of exogenous insulin that is required, may minimize weight gain. In addition, the obese diabetic patient who is poorly controlled with maximum oral hypoglycemic therapy may benefit from weight-reducing agents, such as sibutramine or orlistat. The introduction of these agents at other points in the management of the obese diabetic patients have been successful. Finally, for the severely obese diabetic patient, bariatric surgery may be the only effective treatment. Gastric bypass has been unequivocally shown to produce significant weight loss and improve glycemic control on a long-term basis in the obese diabetic patient. It is recommended that physicians avail themselves of all of these strategies in the management of the obese patient who has type 2 diabetes.

Thiazolidinediones in type 2 diabetes mellitus: current clinical evidence

Type 2 diabetes mellitus is characterised by insulin resistance as well as progressive pancreatic beta cell dysfunction. The cornerstone of current oral blood-glucose lowering therapy consists of metformin, which primarily lowers hepatic glucose production, and the sulphonylureas that act by stimulating pancreatic beta-cells to secrete insulin. Recently, a novel class of agents, the thiazolidinediones, has been introduced that favourably influence insulin sensitivity and possibly also pancreatic beta-cell function. The thiazolidinediones are synthetic ligands that bind to the nuclear peroxisome proliferator-activated receptor-gamma and exert their action by activating transcription of genes that, among others, regulate adipocyte differentiation and adipogenesis as well as glucose and lipid metabolism. To date, the precise mechanisms underlying the actions of thiazolidinediones are largely unknown. When given as monotherapy or in combination with sulphonylureas, metformin or insulin in patients with type 2 diabetes, the currently available thiazolidinediones (rosiglitazone and pioglitazone) ameliorate glycaemic control, by lowering fasting and postprandial blood glucose levels, and improve insulin sensitivity in placebo-controlled trials. They seem to have differential effects on dyslipidaemia in patients with type 2 diabetes; rosiglitazone increases total cholesterol as well as high-density lipoprotein (HDL) and low-density lipoprotein cholesterol levels and affects plasma triglyceride levels depending on the baseline values, whereas pioglitazone lowers triglycerides and increases HDL cholesterol levels. The adverse events of both agents that occur with greater frequency than in patients treated with placebo are fluid retention and oedema. As demonstrated, mainly in preclinical studies to date, rosiglitazone and pioglitazone possess beneficial effects on other cardiovascular risk factors associated with the insulin resistance syndrome. Thus, these agents were shown to decrease blood pressure, enhance myocardial function and fibrinolysis, as well as possess anti-inflammatory and other beneficial vascular effects. Long-term efficacy and surveillance of this promising class of drugs in patients, however, still need to be demonstrated in outcome trials.

Thiazolidinediones and blood lipids in type 2 diabetes

We evaluated study population characteristics and treatment effects on blood lipids between studies in which either rosiglitazone (RSG) or pioglitazone (PIO) was investigated in patients with type 2 diabetes. We performed a summary analysis of all published double-blind, placebo-controlled studies with RSG (4 and 8 mg/d) and PIO (15, 30, and 45 mg/d). Data were analyzed by the random-effects model. Nineteen trials met our inclusion criteria, yielding 5304 patients, 3236 in studies with RSG and 2068 in studies with PIO. Subjects treated with PIO were more obese and showed more pronounced hyperglycemia and dyslipidemia (increased triglycerides and decreased HDL cholesterol) at baseline than did subjects treated with RSG. By weighted linear-regression analysis, studies with PIO showed greater beneficial effects on triglycerides, total cholesterol, and LDL cholesterol, after adjustment for the respective lipid levels at baseline. RSG 8 mg/d showed greater increases in total cholesterol and LDL cholesterol than did RSG 4 mg/d. PIO 30 mg/d showed greater reductions in triglycerides than did PIO 15 mg/d. Studies conducted with PIO showed more beneficial effects on blood lipids, but also different study population characteristics in comparison with studies conducted with RSG. Differences in both pharmacologic properties between agents and study population characteristics are likely to have influenced the results.

The implementation of nutritional advice for people with diabetes

These consensus-based recommendations emphasize the practical implementation of nutritional advice for people with diabetes, and describe the provision of services required to provide the information. Important changes from previous recommendations include greater flexibility in the proportions of energy derived from carbohydrate and monounsaturated fat, further liberalization in the consumption of sucrose, more active promotion of foods with a low glycaemic index, and greater emphasis on the provision of nutritional advice in the context of wider lifestyle changes, particularly physical activity. Monounsaturated fats are now promoted as the main source of dietary fat because of their lower susceptibility to lipid peroxidation and consequent lower atherogenic potential. Consumption of sucrose for patients who are not overweight can be increased up to 10% of daily energy provided that this is eaten in the context of a healthy diet and distributed throughout the day [corrected]. Evidence is presented for the effectiveness of advice provided by trained dieticians. The increasing evidence for the importance of good metabolic control and the growing requirement for measures to prevent Type 2 diabetes in an increasingly obese population will require major expansion of dietetic services if the standards in National Service Frameworks are to be successfully implemented.

The “Glitazones”: Rosiglitazone and Pioglitazone

Rosiglitazone and pioglitazone are two new additions to the therapeutic options for the treatment of type 2 diabetes mellitus. These agents differ from our current therapies in their mode of action. They have potential non-glucose lowering effects that may reduce cardiovascular risk and are effective both as monotherapy and in combination with sulfonylureas, metformin, and insulin. They are generally well tolerated, with the main side effects being weight gain and fluid retention. However, special precaution is warranted in patients with congestive heart failure or hepatic disease, and monitoring of liver enzymes is recommended for the first year of therapy. Despite their effectiveness, rosiglitazone and pioglitazone remain second-line agents to metformin and glyburide, agents that have demonstrated efficacy in decreasing the microvascular and macrovascular complications associated with type 2 diabetes mellitus.

Current management strategies for coexisting diabetes mellitus and obesity

Besides genetic predisposition, obesity is the most important risk factor for the development of diabetes mellitus. Weight reduction has been shown to markedly improve blood glucose control and vascular risk factors associated with insulin resistance in obese individuals with type 2 diabetes. Therapeutic strategies for the obese diabetic patient include: (i) promoting weight loss, through lifestyle modifications (low-calorie diet and exercise) and antiobesity drugs (orlistat, sibutramine, etc.); (ii) improving blood glucose control, through agents decreasing insulin resistance (metformin or thiazolidinediones, e.g. pioglitazone and rosiglitazone) or insulin needs (alpha-glucosidase inhibitors, e.g. acarbose) in preference to agents stimulating defective insulin secretion (sulphonylureas, meglitinide analogues); and (iii) treating common associated risk factors, such as arterial hypertension and dyslipidaemias, to improve cardiovascular prognosis. Whenever insulin is required by the obese diabetic patient after failure to respond to oral drugs, it should be preferably prescribed in combination with an oral agent, more particularly metformin or acarbose, or possibly a thiazolidinedione. When morbid obesity is present, both restoring a good glycaemic control and correcting associated risk factors can only be obtained through a marked and sustained weight loss. This objective justifies more aggressive weight reduction programmes, including very-low-calorie diets and bariatric surgery, but only within a multidisciplinary approach and long-term strategy.

New developments in type 2 diabetes mellitus: combination therapy with a thiazolidinedione

BACKGROUND

Diabetes mellitus (DM) is a serious, chronic metabolic disease affecting approximately 17 million Americans. The microvascular and macrovascular complications of DM are associated with considerable morbidity and mortality.

OBJECTIVES

This article reviews the importance of normalizing blood glucose values to reduce the risk of microvascular and macrovascular complications, discusses available treatment options for type 2 DM, and explores the rationale for combination therapy that includes a thiazolidinedione.

METHODS

Relevant articles were selected from published reports and conference presentations from the last 10 years on oral agents for monotherapy and combination therapy for type 2 DM. Other sources were identified from the reference lists of selected articles.

RESULTS

Choices for the pharmacologic treatment of hyperglycemia in patients with type 2 DM include thiazolidinediones, insulin secretagogues, biguanides, and alpha-glucosidase inhibitors. Each of these drug classes is effective in lowering blood glucose concentrations; however, they have distinctly different mechanisms of action that target various pathophysiologic causes of type 2 DM and have different adverse-event profiles. in addition, several of these agents provide unique benefits unrelated to their hypoglycemic effects. Thiazolidinediones offer the therapeutic benefits of increasing insulin sensitivity and perhaps preserving beta-cell function. Use of a thiazolidinedione from the time type 2 DM is diagnosed improves insulin sensitivity, thereby improving glycemic control and minimizing complications. Over time, however, many patients with type 2 DM are unable to maintain adequate glycemic control (ie, glycosylated hemoglobin [HbA(1c)] <7%) with monotherapy. Combination therapy with agents from different classes may be necessary to achieve blood glucose control through an additive reduction in HbA(1c). The combination of a thiazolidinedione and a biguanide reduces hyperglycemia, hyperinsulinemia, and insulin resistance and improves factors that have been implicated in the pathogenesis of cardiovascular complications.

CONCLUSIONS

Patients with type 2 DM who are not able to maintain their HbA(1c). <7% with monotherapy should be considered candidates for combination therapy. Appropriate combination therapy includes treatment with 2 or more agents with different, complementary mechanisms of action. For example, the combination of a thiazolidinedione and a biguanide improves insulin sensitivity and lowers blood glucose through complementary pathways, and therefore produces an additive effect.

Addition of nateglinide to rosiglitazone monotherapy suppresses mealtime hyperglycemia and improves overall glycemic control

OBJECTIVE

To determine the effects of nateglinide added to rosiglitazone monotherapy on glycemic control and on postprandial glucose and insulin levels in patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS

This 24-week, multicenter, double-blind, randomized study compared the efficacy of nateglinide (120 mg a.c.) and placebo added to rosiglitazone monotherapy (8 mg q.d.) in 402 patients with type 2 diabetes with HbA(1c) between 7 and 11% (inclusive). Efficacy parameters tested included HbA(1c) and plasma glucose and insulin levels in the fasting state and after a standardized meal challenge. Safety data were also collected.

RESULTS

In placebo-treated patients, HbA(1c) did not change (Delta = 0.0 +/- 0.1%). In patients randomized to nateglinide, HbA(1c) decreased from 8.3 to 7.5% (Delta = -0.8 +/- 0.1%, P < 0.0001 vs. placebo). Target HbA(1c) (<7.0%) was achieved by 38% of patients treated with combination therapy and by 9% of patients remaining on rosiglitazone monotherapy. In nateglinide-treated patients, fasting plasma glucose levels decreased by 0.7 mmol/l, 2-h postprandial glucose levels decreased by 2.7 mmol/l, and 30-min insulin levels increased by 165 pmol/l compared with no changes from baseline of these parameters with placebo added to rosiglitazone (P < 0.001).

CONCLUSIONS

By selectively augmenting early insulin release and decreasing prandial glucose excursions, nateglinide produced a clinically meaningful improvement in overall glycemic exposure in patients with type 2 diabetes inadequately controlled with rosiglitazone. Therefore, nateglinide substantially improves the likelihood of achieving a therapeutic target of HbA(1c) <7.0%.

The effect of rosiglitazone on serum lipoprotein(a) levels in Korean patients with type 2 diabetes mellitus

The aim of the study was to determine if rosiglitazone increases serum levels of lipoprotein(a) [Lp(a)] in Korean patients with type 2 diabetes mellitus. A total of 118 patients were divided into 2 groups: those with rosiglitazone (rosiglitazone group, n = 49) and those without rosiglitazone (control group, n = 69). The rosiglitazone group was given rosiglitazone (4 mg/d) with previous treatment, insulin, or sulfonylurea, for 12 weeks, whereas the control group continued previous treatment with some dose modification for glycemic control. The patients had their blood glucose, lipid levels, as well as Lp(a) levels assessed to obtain a baseline, which were remeasured 12 weeks later. The fasting blood glucose and glycosylated hemoglobin (HbA(1c)) levels decreased significantly in both groups as compared with the baseline. The fasting glucose and HbA(1c) levels in both groups were similar at 12 weeks. The total cholesterol levels increased significantly in the rosiglitazone group (190.6 +/- 32.4 to 212.2 +/- 47.2 mg/dL, P =.002), while they were unchanged in the control group (185.4 +/- 36.8 to 188.0 +/- 35.8 mg/dL, P =.615). The triglyceride levels did not change in either group. Significant increases in high-density lipoprotein (HDL) cholesterol levels were observed in the rosiglitazone group as compared with the baseline (41.7 +/- 10.6 to 45.9 +/- 11.4 mg/dL, P =.004). The low-density lipoprotein (LDL) cholesterol levels increased significantly in the rosiglitazone group (120.5 +/- 29.9 to 136.3 +/- 40.0 mg/dL, P =.012), while they did not change in the control group (113.0 +/- 29.1 to 118.3 +/- 31.7 mg/dL, P =.234). Significant increases in Lp(a) levels were observed in the rosiglitazone group as compared with the baseline (22.4 +/- 17.4 to 25.7 +/- 20.5 mg/dL, P =.015), approximately a 15% increase in average values. In contrast, there was no change in Lp(a) levels in the control group. There was no correlation between the changes in Lp(a) and changes in fasting blood glucose or HbA(1c) levels in all study subjects. In summary, rosiglitazone increased serum total cholesterol, LDL cholesterol, as well as Lp(a) levels in patients with type 2 diabetes mellitus. Considering that patients with type 2 diabetes mellitus have increased risks for cardiovascular disease, caution should be taken when prescribing rosiglitazone to patients who already have other risk factors, such as hypertension and smoking.

Effects of thiazolidinediones on cardiovascular risk factors

The thiazolidinediones are the insulin sensitizers used in the management of Type 2 diabetes mellitus. These drugs can potentially decrease the risk of cardiovascular disease by correcting the different components of the insulin resistance syndrome.

Pharmacological management of type 2 diabetes mellitus: rationale for rational use of insulin

Type 2 diabetes mellitus is a chronic metabolic disorder associated with high morbidity and mortality from long-term microvascular and macrovascular complications. Evidence from randomized controlled trials indicates that aggressive treatment directed at improving glycemic control reduces the incidence of diabetes-related microvascular complications. Traditionally, oral monotherapy for type 2 diabetes is initiated when diet and exercise do not control hyperglycemia, followed by the sequential, stepwise addition of oral agents as glycemic control deteriorates. Insulin is the last therapeutic option used, generally reserved for advanced stages of the disease when multiple oral combination treatment fails. Despite a better understanding of the pathophysiologic disease mechanisms in the past decade, the expanded armamentarium of targeted oral antidiabetic drugs, and the conclusive evidence of the benefits of stringent glycemic control, actual treatment outcomes in clinical practice remain suboptimal relative to established treatment goals (glycosylated hemoglobin A1c level <7%). Earlier detection and aggressive treatment are critical to address the natural progression of diabetes because multiple defects (insulin resistance, insulin insufficiency, glucotoxicity, and lipotoxicity) and vascular complications may be present at the time of diagnosis. Acknowledging the inadequacy of traditional strategies and underscoring the importance of insulin as an integral part of the therapeutic armamentarium, clinical trends are moving toward earlier use of insulin combined with 1 or more oral agents. Such strategies can address the multiple abnormalities present early in the disease course and may restore optimal control. A new treatment paradigm for patients with type 2 diabetes to achieve and maintain near-normal glycemic control is warranted.

Insulin sensitizers

Type 2 diabetes mellitus is an increasingly prevalent disorder associated with multiple metabolic derangements. Insulin resistance is the most prominent feature common in both type 2 diabetes and its associated metabolic abnormalities. Until 1995, the only therapeutic interventions available in the United States were the insulin secretagogues sulfonylureas and insulin. With the introduction of metformin in the United States in the mid-1990s and the subsequent advent of thiazolidinediones, an opportunity exists to address and directly reverse, at least in part, the defects in insulin action seen in individuals with type 2 diabetes. Evidence shows that insulin sensitizers not only have beneficial effects on glycemic control but also have multiple effects on lipid metabolism and atherosclerotic vascular processes that could prove to be beneficial. We discuss safety issues of these agents, their potential use in preventing onset and progression of diabetes, and their use in other related metabolic conditions such as polycystic ovary syndrome.

Insulin sensitisation in the treatment of Type 2 diabetes

Type 2 diabetes is reaching epidemic proportions worldwide, fueled by the increasing prevalence of obesity as many populations adopt a western lifestyle. Secondary complications affecting both the microvascular and macrovascular systems are responsible for premature mortality in Type 2 diabetes, with two thirds or more dying of cardiovascular disease. Two interacting metabolic defects, insulin resistance and beta-cell dysfunction are present in Type 2 diabetes. It is now recognised that insulin resistance is central to a cluster of metabolic abnormalities--called the insulin resistance syndrome--that are responsible for the excess of cardiovascular disease. Older antidiabetic agents such as the sulfonylureas, metformin and insulin are more effective than lifestyle modification in reducing microvascular complications of Type 2 diabetes, but overall do not reduce cardiovascular risk. Metformin, although no more effective as a glucose-lowering agent than sulfonylureas or insulin, does significantly reduce cardiovascular disease, probably as a result of its weak insulin-sensitising action. The newly-marketed thiazolidinedione insulin-sensitising antidiabetic agents also improve multiple biomarkers of cardiovascular risk, suggesting that novel approaches to insulin sensitisation will not only provide effective long-term glycaemic control but improve cardiovascular outcomes in Type 2 diabetes. Multiple therapeutic targets within the insulin signalling cascade are being explored, together with follow-up compounds to the first generation thiazolidinediones. These initiatives, together with developments in beta(3)-adrenoceptor agonists, 11 beta-hydroxysteroid dehydrogenase Type 1 inhibitors and modulators of the glucagon-like peptide 1 axis, all of which also potentially enhance insulin sensitivity, are critically evaluated.

Differential effects of rosiglitazone and metformin on adipose tissue distribution and glucose uptake in type 2 diabetic subjects

We evaluated the effects of rosiglitazone (4 mg b.i.d.) and metformin (1 g b.i.d.) monotherapy for 26 weeks on adipose tissue insulin-stimulated glucose uptake in patients (n = 41) with type 2 diabetes. Before and after the treatment, glucose uptake was measured using 2-[(18)F]fluoro-2-deoxyglucose and positron emission tomography and adipose tissue masses were quantified using magnetic resonance imaging. Rosiglitazone improved insulin-stimulated whole-body glucose uptake by 44% (P < 0.01 vs. placebo). Mean body weight was unchanged in the rosiglitazone group, while it decreased by 2.0 kg in the metformin group (P < 0.05 vs. placebo). In visceral adipose tissue, glucose uptake increased by 29% (from 17.8 +/- 2.0 to 23.0 +/- 2.6 micro mol x kg(-1) x min(-1), P < 0.05 vs. placebo) in the rosiglitazone group but to a lesser extent (17%) in the metformin group (from 16.2 +/- 1.5 to 18.9 +/- 1.7 micro mol x kg(-1) x min(-1), P < 0.05 vs. baseline). Because the visceral adipose tissue mass simultaneously decreased with both treatments (P < 0.05), no change was observed in total visceral glucose uptake per depot. Rosiglitazone significantly enhanced glucose uptake in the femoral subcutaneous area, either when expressed per tissue mass (from 10.8 +/- 1.2 to 17.1 +/- 1.7 micro mol x kg(-1) x min(-1), P < 0.01 vs. placebo) or per whole-fat depot (P < 0.05 vs. placebo). In conclusion, metformin treatment resulted in improvement of glycemic control without enhancement of peripheral insulin sensitivity. The improved insulin sensitivity of the nonabdominal subcutaneous adipose tissue during treatment with rosiglitazone partly explains the enhanced whole-body insulin sensitivity and underlies the central role of adipose tissue for action of peroxisome proliferator-activated receptor gamma agonist in vivo.

Type 2 diabetes, cardiovascular risk, and the link to insulin resistance

BACKGROUND

Patients with type 2 diabetes mellitus frequently have coexistent dyslipidemia, hypertension, and obesity, and are at risk for microvascular and macrovascular disease complications such as myocardial infarction, stroke, retinopathy, and microalbuminuria. To optimize cardiovascular health outcomes for patients with type 2 diabetes, strategies to reduce the risks of microvascular and macrovascular disease are needed in clinical practice.

OBJECTIVE

This article provides an overview of the cardiovascular risk profile of patients with type 2 diabetes and discusses the cardiovascular consequences of use of the thiazolidinediones (insulin-sensitizing agents) in the treatment of type 2 diabetes.

METHODS

A literature search of MEDLINE/PubMed was performed to identify relevant articles published from 1966 to April 2003. Search terms used were diabetes, cardiovascular disease, atherosclerosis, dyslipidemia, obesity, hypertension, blood pressure, hyperglycemia, inflammation, C-reactive protein, fibrinolysis, plasminogen activator inhibitor type-1, microalbuminuria, thiazolidinediones, safety, hepatotoxicity, and edema. Bibliographies within the identified articles were also evaluated for additional relevant articles and information.

RESULTS

Recommendations for cardiovascular risk reduction through preventive and therapeutic strategies that target the symptoms of insulin resistance may reduce the microvascular and macrovascular sequelae of diabetes and ameliorate the impact of other components of the metabolic syndrome, including hypertension, hyperglycemia, and obesity. In this regard, thiazolidinediones are promising therapies.

CONCLUSIONS

Early data suggest that, in addition to reducing hyperglycemia, pioglitazone and rosiglitazone effect changes in the dyslipidemic profile, hemodynamics, vascular inflammation, and endothelial functioning of patients with type 2 diabetes. Additional research is needed to further distinguish the cardiovascular benefits of these drugs.

Multicenter retrospective assessment of thiazolidinedione monotherapy and combination therapy in patients with type 2 diabetes: Comparative subgroup analyses of glycemic control and blood lipid levels

BACKGROUND

Thiazolidinediones (TZDs) have contributed to the management of patients with type 2 diabetes mellitus as unique insulin-sensitizing agents. When used as monotherapy or in combination therapy, these drugs not only reduce glycosylated hemoglobin (HbA(1c)) levels, but also effect changes in blood lipid concentrations and have the potential to ameliorate cardiovascular disease risk. Although drugs in the TZD class are perceived to be equivalent clinically, prospective and retrospective studies have demonstrated their ability to modify blood lipid levels.

OBJECTIVE

We evaluated and compared the effects of pioglitazone and rosiglitazone monotherapy and combination therapy on blood lipid levels and HbA(1c) in patients with type 2 diabetes.

METHODS

We conducted a multicenter retrospective chart review of 1115 records of patients with type 2 diabetes who received pioglitazone or rosiglitazone, alone or in combination with other antidiabetic agents, between August 1, 1999, and August 31, 2000. The review was conducted to evaluate pretreatment and posttreatment levels of triglyceride, total cholesterol, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and HbA(1c).

RESULTS

All observed demographic characteristics, comorbidities, and concomitant drug use were similar in both treatment cohorts. Of the patients who received pioglitazone, 83% also received >/=1 other antihyperglycemic agent and 59% received some form of antihyperlipidemic therapy. Among those who received rosiglitazone, 81% received concomitant antihyperglycemic medication and 60% received some form of antihyperlipidemic therapy. With pioglitazone, mean levels of serum triglyceride, total cholesterol, and LDL-C decreased and HDL-C increased in most patients, with or without concomitant antihyperglycemic medications; with rosiglitazone, with or without other antidiabetic agents, triglyceride and HDL-C levels decreased, whereas total cholesterol and LDL-C levels increased in most patients. Reductions in HbA(1c) levels and increases in body weight related to each study drug were comparable.

CONCLUSIONS

This comparative assessment of pioglitazone and rosiglitazone, based on observational data, reveals that use of these TZDs with other antidiabetic agents was similar in 605 primary care practices in the United States. In both monotherapy and combination treatment regimens, pioglitazone was associated with greater beneficial effects on lipids than was rosiglitazone. Additional studies are needed to determine the long-term outcomes of TZD therapy with concomitant antihyperglycemic medications.

PPAR(gamma) and glucose homeostasis

Peroxisome proliferator-activated receptor gamma (PPARgamma) is a nuclear receptor involved in the control of metabolism. Research on PPARgamma is oriented towards understanding its role in insulin sensitization, which was inspired by the discovery that antidiabetic agents, the thiazolidinediones, were agonists for PPARgamma. PPARgamma stimulation improves glucose tolerance and insulin sensitivity in type 2 diabetic patients and in animal models of insulin resistance through mechanisms that are incompletely understood. Upon activation, PPARgamma heterodimerizes with retinoid X receptor, recruits specific cofactors, and binds to responsive DNA elements, thereby stimulating the transcription of target genes. Because PPARgamma is highly enriched in adipose tissue and because of its major role in adipocyte differentiation, it is thought that the effects of PPARgamma in adipose tissue are crucial to explain its role in insulin sensitization, but recent studies have highlighted the contribution of other tissues as well. Although relatively potent for their insulin-sensitizing action, currently marketed PPARgamma activators have some important undesirable side effects. These concerns led to the discovery of new ligands with potent antidiabetic properties but devoid of certain of these side effects. Data from human genetic studies and from PPARgamma heterozygous knockout mice indicate that a reduction in PPARgamma activity could paradoxically improve insulin sensitivity. These findings suggest that modulation of PPARgamma activity by partial agonists or compounds that affect cofactor recruitment might hold promise for the treatment of insulin resistance.

Rosiglitazone: a review of its use in the management of type 2 diabetes mellitus

Rosiglitazone, a thiazolidinedione with a different side chain from those of troglitazone and pioglitazone, reduces plasma glucose levels and glucose production and increases glucose clearance in patients with type 2 diabetes mellitus. Insulin sensitivity, pancreatic beta-cell function and surrogate markers of cardiovascular risk factors are significantly improved by rosiglitazone. Double-blind trials of 8 to 26 weeks of rosiglitazone 4 or 8 mg/day monotherapy indicate significant decreases in fasting plasma glucose (-2 to -3 mmol/L with 8 mg/day) and glycosylated haemoglobin levels [HbA(1c); -0.6 to -0.7% (-0.8 to -1.1% in drug-naive patients) with 8 mg/day]. Significant decreases in hyperglycaemic markers occurred when rosiglitazone was combined with metformin (HbA(1c) -0.8 to -1.0%), a sulphonylurea (-1.4%) or insulin (-1.2%) for 26 weeks versus little change with active comparator monotherapy. Efficacy was maintained in trials of < or = 2 years, and was also apparent in various ethnic subgroups, elderly patients, and both obese and nonobese patients. Rosiglitazone is currently not indicated in combination with injected insulin. It should be administered in conjunction with diet and exercise regimens. Rosiglitazone is generally well tolerated. Despite rare individual reports of liver function abnormalities in rosiglitazone recipients, the incidence of these in clinical trials (< or = 2 years' duration) was similar to that in placebo and active comparator groups. Fluid retention associated with rosiglitazone may be the cause of the increased incidence of anaemia in clinical trials, and also means that patients should be monitored for signs of heart failure during therapy. Although bodyweight is increased overall with rosiglitazone therapy, increases are in subcutaneous, not visceral, fat; hepatic fat is decreased. The pharmacokinetic profile of rosiglitazone is not substantially altered by age or renal impairment, nor are there important drug interactions. Rosiglitazone is not indicated in patients with active liver disease or increased liver enzymes.

CONCLUSIONS

Oral rosiglitazone 4 or 8 mg/day provides significant antihyperglycaemic efficacy and is generally well tolerated, both as monotherapy and in combination with other antihyperglycaemic agents, in patients with type 2 diabetes mellitus who do not have active liver disease. Long-term data are required before conclusions can be drawn about the clinical significance of positive changes to surrogate markers of cardiovascular disease risk and improvements to pancreatic beta-cell function. Rosiglitazone significantly improves insulin sensitivity and, as such, is a welcome addition to the treatment options for patients with type 2 diabetes mellitus.

Reappraisal of the pharmacologic approach to treatment of type 2 diabetes mellitus

Nearly 16 million adults in the United States have diabetes mellitus, and the incidence of type 2 diabetes, the most prevalent form of diabetes, has steadily increased during the past decade. Patients with diabetes are at increased risk for microvascular and macrovascular complications and experience significant morbidity and mortality. Diabetes is the leading cause of blindness, end-stage renal disease, and nontraumatic amputations in adults. Because diabetes is a progressive disorder, the importance of early and appropriate treatment cannot be overemphasized. Present therapeutic strategies for the management of type 2 diabetes are adequate but are not maximally effective. Clearly, reappraisal of the pharmacologic approach to the optimal management of patients with type 2 diabetes is needed. A number of oral hypoglycemic agents, including thiazolidinediones, biguanides, sulfonylureas, and alpha-glucosidase inhibitors, may be used to normalize glucose levels in patients with type 2 diabetes. Because insulin resistance is an underlying pathologic defect in patients with type 2 diabetes, agents that increase insulin sensitivity should be used early in the course of therapy. By using a multifaceted approach to target insulin resistance, many patients with type 2 diabetes may achieve normoglycemia and improved long-term outcomes.

Rationale for and role of thiazolidinediones in type 2 diabetes mellitus

Several classes of antihyperglycemic agents are available for the treatment of patients with type 2 diabetes. These agents, including thiazolidinediones, biguanides, insulin secretagogues, alpha-glucosidase inhibitors, and insulin, offer differing mechanisms of actions and can be used either alone or in combination. The thiazolidinediones are a newer class of oral antidiabetic agents that improve glycemic control and may preserve beta-cell function. Clinical trial data suggest that patients with type 2 diabetes experience progressive deterioration of beta-cell function. By decreasing insulin resistance, thiazolidinediones may preserve beta-cell function, and patients may experience prolonged glycemic control. The thiazolidinediones also exert beneficial effects on dyslipidemia, endothelial function, coagulation, and blood pressure. By improving these components of the metabolic syndrome, thiazolidinediones may reduce the incidence of both microvascular and macrovascular complications. This article provides an overview of the role of thiazolidinediones in the treatment of type 2 diabetes.

Metabolic and additional vascular effects of thiazolidinediones

Several cardiovascular risk factors (dyslipidaemia, hypertension, glucose intolerance, hypercoagulability, obesity, hyperinsulinaemia and low-grade inflammation) cluster in the insulin resistance syndrome. Treatment of these individual risk factors reduces cardiovascular complications. However, targeting the underlying pathophysiological mechanisms of the insulin resistance syndrome is a more rational treatment strategy to further improve cardiovascular outcome. Our understanding of the so-called cardiovascular dysmetabolic syndrome has been improved by the discovery of nuclear peroxisome proliferator-activated receptors (PPARs). PPARs are ligand-activated transcription factors belonging to the nuclear receptor superfamily. As transcription factors, PPARs regulate the expression of numerous genes and affect glycaemic control, lipid metabolism, vascular tone and inflammation. Activation of the subtype PPAR-gamma improves insulin sensitivity. Expression of PPAR-gamma is present in several cell types involved in the process of atherosclerosis. Thus, modulation of PPAR-gamma activity is an interesting therapeutic approach to reduce cardiovascular events. Thiazolidinediones are PPAR-gamma agonists and constitute a new class of pharmacological agents for the treatment of type 2 (non-insulin-dependent) diabetes mellitus. Two such compounds are currently available for clinical use: rosiglitazone and pioglitazone. Thiazolidinediones improve insulin sensitivity and glycaemic control in patients with type 2 diabetes. In addition, improvement in endothelial function, a decrease in inflammatory conditions, a decrease in plasma levels of free fatty acids and lower blood pressure have been observed, which may have important beneficial effects on the vasculature. Several questions remain to be answered about PPAR-gamma agonists, particularly with respect to the role of PPAR-gamma in vascular pathophysiology. More needs to be known about the adverse effects of thiazolidinediones, such as hepatotoxicity, increased low-density lipoprotein cholesterol levels and increased oedema. The paradox of adipocyte differentiation with weight gain concurring with the insulin-sensitising effect of thiazolidinediones is not completely understood. The decrease in blood pressure induced by thiazolidinedione treatment seems incompatible with an increase in the plasma volume, and the discrepancy between the stimulation of the expression of CD36 and the antiatherogenic effects of the thiazolidinediones also needs further explanation. Long-term clinical trials of thiazolidinediones with cardiovascular endpoints are currently in progress. In conclusion, studying the effects of thiazolidinediones may shed more light on the mechanisms involved in the insulin resistance syndrome. Furthermore, thiazolidinediones could have specific, direct effects on processes involved in the development of vascular abnormalities.

Isoflavones from red clover (Promensil) significantly reduce menopausal hot flush symptoms compared with placebo

OBJECTIVES

To investigate the effectiveness and safety of a red clover isoflavone dietary supplement (Promensil, Novogen Ltd., Australia) versus placebo on the change in hot flush frequency in postmenopausal women.

METHODS

In this randomized, double blind, placebo-controlled trial 30 women with more than 12 months amenorrhoea and experiencing more than five flushes per day were enrolled. All received single blind placebo tablets for 4 weeks and were subsequently randomized to either placebo or 80 mg isoflavones for a further 12 weeks. Efficacy was measured by the decrease in number of hot flushes per day and changes in Greene Climacteric Scale Score.

RESULTS

During the first 4 weeks of placebo the frequency of hot flushes decreased by 16%. During the subsequent double blind phase, a further, statistically significant decrease of 44% was seen in isoflavones group (P<0.01), whereas no further reduction occurred within the placebo group. The Greene score decreased in the active group by 13% and remained unchanged in the placebo group.

CONCLUSION

In this study, treatment with 80 mg isoflavones (Promensil) per day resulted in a significant reduction in hot flushes from baseline. At the end of the study there was a significant decrease in hot flushes of 44% between the active and placebo group, demonstrating the effectiveness of Promensil in the management of hot flushes.

Rosiglitazone amplifies the benefits of lifestyle intervention measures in long-standing type 2 diabetes mellitus

AIMS

To evaluate the efficacy of a lifestyle intervention programme including meal replacements and increased physical activity upon body weight, diabetes control and other cardiovascular risk factors in obese, poorly controlled, insulin-treated, type-2-diabetic individuals and to assess the impact of concomitant rosiglitazone (RSG) therapy.

METHODS

This 6-month intervention study included 21 patients with type 2 diabetes mellitus (DM) requiring insulin therapy with haemoglobin A1c (HbA1c) > 7% and with a body mass index (b.m.i.) > 27. All subjects were enrolled in a 6-month lifestyle intervention programme and randomized to placebo or RSG 4 mg/day. Participation in the lifestyle programme included meal replacements, increased intake of fruits and vegetables and increased daily physical activity. Measured end-points included body weight, waist circumference, blood pressure, HbA1c and serum lipids, before entry into the study.

RESULTS

The baseline mean b.m.i. was 36.4 and the mean HbA1c was 9.0%. The greatest weight losses occurred during the first 12 weeks (19 lbs for RSG, 13.4 lbs for placebo) with a greater weight loss at each point for the group receiving RSG. Waist circumference declined by 2.8 and 4.0 inches for the placebo and RSG groups. Systolic BP declined 16.2 mmHg in the placebo group and 14.3 mmHg in the RSG group. Diastolic blood pressure decreased by 12.8 mmHg in the placebo group. HbA1c was reduced significantly by 1.3% for the placebo group and 1.1% in the RSG group.

DISCUSSION

This study demonstrates the benefits of lifestyle intervention using meal replacements and increased physical activity with resultant modest weight loss in long-standing, poorly controlled type 2 diabetes. RSG did not impede weight loss and, in fact, amplified some of the positive benefits of lifestyle intervention.

Thiazolidinedione therapy in a patient with diabetes after cardiac transplantation

OBJECTIVE

To describe the successful use of a thiazolidinedione agent for the treatment of diabetes diagnosed after heart transplantation.

METHODS

We present a case report of a 51-year-old woman who underwent cardiac transplantation because of cardiomyopathy; diabetes developed 6 months later. Her clinical course and serial laboratory findings are documented as insulin therapy was initiated and subsequently transitioned to rosiglitazone during maintenance of the immunosuppressive regimen.

RESULTS

After rosiglitazone therapy was instituted, the patient's insulin dose was gradually tapered and eventually stopped. Target glycemic control was maintained without apparent aggravation of cardiac function or volume overload. No deleterious effects on other organ systems or interactions with the antirejection medications were noted during close follow-up.

CONCLUSION

Rosiglitazone may be safe and effective therapy for patients with posttransplantation diabetes. Rosiglitazone also helps to counteract the insulin-resistant state and reduces or eliminates the need for exogenous insulin. Further studies should attempt to confirm the usefulness of treatment with thiazolidinediones for patients with diabetes after organ transplantation.

Combination of insulin and thiazolidinedione therapy in massively obese patients with Type 2 diabetes

AIMS

To evaluate the influence of addition of rosiglitazone to insulin therapy over a 24-week period in massively obese patients with poorly controlled Type 2 diabetes taking large doses of insulin.

METHODS

Eight massively obese patients (median body mass index (BMI) 42 kg/m2) with Type 2 diabetes who were on large doses of insulin (median daily dose of 204 U) and/or had poor glycaemic control (median HbA1c of 8.1% (upper limit for normal 5.5%)) were treated over a 24-week period with the combination of insulin and maximum doses of rosiglitazone. Outcomes monitored were changes in weight, BMI, HbA1c, dose of insulin and development of side-effects.

RESULTS

At the end of 24 weeks there was a median weight gain of 3 kg (P < 0.01), a fall in median HbA1c from 8.1% to 6.7% (16% reduction from baseline) (P < 0.01) and a reduction in median insulin dose from 204 U/day to 159 U/day (P < 0.01) (23% reduction from baseline). Peripheral oedema was the only significant side-effect and was seen in five patients.

CONCLUSIONS

Combination of insulin and rosiglitazone is effective in massively obese patients with Type 2 diabetes, though there is a high incidence of peripheral oedema.

Thiazolidinediones and type 2 diabetes: new drugs for an old disease

Thiazolidinediones are a new class of drugs for the treatment of type 2 diabetes, and act by improving insulin sensitivity in adipose tissue, liver and skeletal muscle. Rosiglitazone and pioglitazone are registered for use in monotherapy, and in combination with sulfonylureas and metformin. Pioglitazone is also licensed for use in combination with insulin. There is level II evidence that in patients with inadequate glycaemic control both drugs reduce the level of HbA1c and fasting plasma glucose (FPG) when used as monotherapy and in combination with sulfonylurea or metformin or insulin; and both drugs increase levels of HDL and LDL and lower free fatty acid levels, but only pioglitazone significantly lowers triglyceride levels. Both drugs lower fasting insulin and C-peptide levels. In monotherapy, they may be slightly less potent at reducing the level of HbA1c than sulfonylureas or metformin. The maximal effect of these agents may not be seen for 6-14 weeks after commencement. Both drugs are well tolerated but liver function must be checked at baseline every second month for the first year, and periodically thereafter. The drugs are currently contraindicated in patients with moderate to severe liver dysfunction and alanine aminotransferase levels more than 2.5 times normal, New York Heart Association III-IV cardiac status, pregnancy, lactation and in children. The main side effects include weight gain, oedema, and mild dilutional anaemia.

Rosiglitazone in the Treatment of Haart-Associated Lipodystrophy – a Randomized Double-Blind Placebo-Controlled Study

Highly active antiretroviral therapy (HAART) is associated with metabolic adverse events such as insulin resistance and lipodystrophy, that is, atrophy of subcutaneous fat and accumulation of intra-abdominal fat. Currently, there is no pharmacological treatment for lipoatrophy. Glitazones, a novel class of insulin-sensitizing anti-diabetic agents, increase subcutaneous fat in patients with type 2 diabetes. There are no controlled studies of glitazones in patients with HAART-associated lipodystrophy (HAL). In this randomized, double-blind, placebo-controlled study, 30 patients with HAL received either rosiglitazone (8 mg daily) or placebo for 24 weeks. Baseline characteristics were compared to a group of 30 age-, sex- and weight-matched HIV-negative controls. At baseline, patients with HAL had 1.8-fold (P<0.001) more intra-abdominal and 2.4-fold (P<0.05) more liver fat than HIV-negative controls, who had 1.8-fold (P<0.001) more subcutaneous fat than the patients. After 24 weeks of treatment, rosiglitazone had no effect on body weight, subcutaneous or intra-abdominal fat (magnetic resonance imaging), total body fat (bioimpedance analysis), anthropometric measurements or serum leptin concentrations (a circulating marker of adipose tissue mass). However, rosiglitazone decreased % liver fat (spectroscopy) and serum insulin concentrations, and normalized liver function tests. During the first 12 weeks of rosiglitazone treatment, serum triglycerides increased from 3.5 ±0.5 to 6.5 ±2.0 mmol/l (from 310 ±44 to 575 ±177 mg/dl) (P<0.05) and serum cholestrol from 6.0 ±0.4 to 7.8 ±0.7 mmol/l (from 232 ±15 to 301 ±27 mg/dl) (P<0.01). Contrary to data in other patient groups, rosiglitazone did not increase subcutaneous fat in patients with HAL after 24 weeks of treatment. Rosiglitazone seemed to ameliorate insulin resistance judged by the decreased serum insulin concentrations and % liver fat. Rosiglitazone unexpectedly caused significant increases in serum triglyceride and cholesterol concentrations, which must be carefully monitored if glitazones are used in these patients.

Effects of pioglitazone and rosiglitazone on blood lipid levels and glycemic control in patients with type 2 diabetes mellitus: a retrospective review of randomly selected medical records

BACKGROUND

The antihyperglycemic effects of pioglitazone hydrochloride and rosiglitazone maleate are well documented. The results of clinical trials and observational studies have suggested, however, that there are individual differences in the effects of these drugs on blood lipid levels.

OBJECTIVE

The present study evaluated the effects of pioglitazone and rosiglitazone on blood lipid levels and glycemic control in patients with type 2 diabetes mellitus.

METHODS

This was a retrospective review of randomly selected medical records from 605 primary care practices in the United States in which adults with type 2 diabetes received pioglitazone or rosiglitazone between August 1, 1999, and August 31, 2000. The outcome measures were mean changes in serum concentrations of triglycerides (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and glycosylated hemoglobin (HbA1c) values.

RESULTS

Treatment with pioglitazone was associated with a reduction in mean TG of 55.17 mg/dL, a reduction in TC of 8.45 mg/dL, an increase in HDL-C of 2.65 mg/dL, and a reduction in LDL-C of 5.05 mg/dL. Treatment with rosiglitazone was associated with a reduction in mean TG of 13.34 mg/dL, an increase in TC of 4.81 mg/dL, a reduction in HDL-C of 0.12 mg/dL, and an increase in LDL-C of 3.56 mg/dL. With the exception of HDL-C, the differences in mean changes in lipid parameters between treatment groups were statistically significant (P < 0.001, pioglitazone vs rosiglitazone). Reductions in HbA1c were statistically equivalent between treatments (1.04% pioglitazone, 1.18% rosiglitazone).

CONCLUSIONS

Treatment with pioglitazone was associated with greater beneficial effects on blood lipid levels than treatment with rosiglitazone, whereas glycemic control was equivalent between the 2 treatments.

Management of rosiglitazone-induced edema: two case reports and a review of the literature

The thiazolidinediones are an important class of insulin-sensitizing agents used for the treatment of type 2 diabetes. Similar to other antidiabetic agents, use of the thiazolidinediones is limited by adverse drug reactions. Specifically, use of the thiazolidinediones is associated with a triad of fluid retention, edema, and weight gain. In premarketing clinical trials, edema was reported to occur infrequently with minimal severity. However, several published cases from postmarketing data demonstrate that thiazolidinedione-induced fluid retention, exhibited by the initial onset of peripheral edema and weight gain, can progress to a more severe form of pulmonary edema that is refractory to diuretic therapy with resolution of symptoms only through discontinuation of the offending thiazolidinedione. In clinical practice, the occurrence of edema secondary to a thiazolidinedione drug may occur more frequently than reported. Two cases presented in this report illustrate a different outpatient management approach that enables both desired glycemic control and minimal fluid retention while using the thiazolidinediones.

An international study of the effects of rosiglitazone plus sulphonylurea in patients with type 2 diabetes

This was an open-label, randomised 26-week study to determine the effects of adding 4 mg rosiglitazone (Avandia) daily to existing sulphonylurea (SU) therapy in patients with type 2 diabetes from India, Brazil, The Philippines, Thailand, Argentina and Tunisia. Of the 348 patients, 175 received 2 mg rosiglitazone twice daily plus SU (RSG+SU) and 173 received SU alone (at their normal dose). The RSG+SU group showed a significant reduction in HbA1c (mean HbA1c 9.05% at baseline, 7.92% at 26 weeks, mean change -1.13 (95% Cl -1.37, -0.89)). Mean HbA1c essentially remained unchanged in the control group (8.9 to 9.0%). The RSG+SU group showed a significant decrease in fasting plasma glucose concentration (FPG) (mean FPG 198.7 mg/dl at baseline, 160.3 mg/dl at 26 weeks, mean change -38.4 (95% Cl -47.1, -29.7)) while the controls showed a non-significant increase from 194 to 200 mg/dl. Significantly more patients in the RSG+SU group achieved FPG < 140 mg/dl, > or = 0.7% decrease in HbA1c, and > or = 30 mg/dl decrease in FPG between baseline and week 26 than the controls (p = 0.0001 in each case). Adverse events were similar in both groups; more patients in the RSG+SU group reported hypoglycaemia, but most cases were mild. This study shows that adding rosiglitazone to existing SU treatment improves glycaemic control and is well-tolerated in patients with type 2 diabetes from a wide range of non-Western countries.

Current literature in diabetes

In order to keep subscribers up-to-date with the latest developments in their field, John Wiley & Sons are providing a current awareness service in each issue of the journal. The bibliography contains newly published material in the field of diabetes/metabolism. Each bibliography is divided into 17 sections: 1 Books, Reviews & Symposia; 2 General; 3 Genetics; 4 Epidemiology; 5 Immunology; 6 Prediction; 7 Prevention; 8 INTERVENTION: a&rpar General; b&rpar Pharmacology; 9 Pathology: a&rpar General; b&rpar Cardiovascular; c&rpar Neurological; d&rpar Renal; 10 Endocrinology & Metabolism; 11 Nutrition; 12 Animal Studies; 13 Techniques. Within each section, articles are listed in alphabetical order with respect to author (9 Weeks journals - Search completed at 1st Aug 2001)